Method and system for oversubscribing bandwidth in a communications network

ABSTRACT

A method and system for oversubscribing bandwidth in a communication network, is disclosed. The method comprises receiving data flow from a plurality of sources in an oversubscription module in the network, wherein the oversubscription module comprises a plurality of entry meters and at least one oversubscription meter. The method further includes policing in an entry meter the data flow from a source and generating an output flow, wherein the entry meter enforces a service agreement between the source and the network, policing the output flow from the entry meter in the at least one oversubscription meter, wherein the oversubscription meter enforces an oversubscription flow agreement, and generating an output flow from the at least one oversubscription meter that is transmitted through the network.

FIELD OF THE INVENTION

[0001] The present invention relates to resource management in acommunication network and more particularly to a method and system foroversubscribing bandwidth in a communication network.

BACKGROUND OF THE INVENTION

[0002] Advances in communication technology have transformed theInternet in a true information super highway. Scores of communicationnetworks, shared and private, interconnect with one another to providetraffic paths between users. A shared network provides communicationservices to all users, such as corporations and individuals, willing tosubscribe, and is maintained by a service provider. As the number ofusers increases, the service provider must invest in new equipment tomeet the needs of its customers. This is particularly true if theservice provider offers guaranteed levels of service for customers whodemand certain levels of bandwidth.

[0003] Because capital expenditures are costly and therefore, generallyavoided, service providers strive to maximize utilization of theirexisting resources, while minimizing traffic congestion. One way ofachieving this goal is for the service provider to oversubscribe itsservice to its customers, i.e., reserving fewer resources than the sumof what each user is requesting. The underlying assumption foroversubscription is that the probability of all (or a large proportionof) users requesting service at the same time is statistically low.Therefore, the service provider should be able to expand its user base,while maintaining an acceptable level of service without necessarilyexpanding its network resources.

[0004] In a connection-oriented network, e.g., an Asynchronous TransferMode (ATM) network, each user of the network must create a connection totransmit and receive traffic. When the connection is created, somenetwork resources, such as bandwidth, processing power and memory, areallocated and reserved for this connection. This constitutes anagreement between the user and the network's service provider. Theservice provider must enforce this agreement during the lifetime of theconnection. Oversubscription in such an environment is common andrelatively straightforward because network resources are reserved priorto the transmission of data.

[0005] In a connection-less network, e.g., an IP network such as theInternet, a service provider should also have the ability to reservenetwork resources for its users, except that a pre-establishedconnection is not utilized. Instead, each packet transmitted from andreceived by a given user is identified, e.g., encoded, such that theservice provider can determine from the packet its priority level andreserve the necessary network resources to enforce the agreement.Oversubscription in a connection-less network environment is complicatedbecause network resources are reserved when traffic flow arrives at thenetwork, and not prior to transmission. If the network is operating at,or near, capacity, the service provider can have difficulties providingpromised levels of service for its customers, thereby impacting thequality of service.

[0006] For example, if a user wishes to send and receive realtime voiceand video data, i.e., Constant Bit Rate (CBR) traffic, the serviceprovider can agree to guarantee a certain level of bandwidth for theuser's traffic. The agreed level of guaranteed bandwidth is referred toas a Committed Information Rate (CIR), and data flow within this rangewould be considered high priority. If the network is oversubscribed, theservice provider cannot guarantee that high priority flow will betransmitted in the place of low priority flow, such as Unspecified BitRate (UBR) or Best Effort (BE) traffic. Thus, oversubscription can causeserious erosion in a provider's quality of service.

[0007] Most oversubscription methods for both connection-oriented andconnection-less networks are based on static models that are networkspecific, or complex statistical models that are generally difficult toimplement. In addition, most oversubscription methods cover only asingle level of oversubscription.

[0008] Accordingly, a need exists for an improved system and method foroversubscribing bandwidth in connection-oriented and connection-lesscommunication networks. The system and method should ensure that highpriority flow is given precedence over low priority flow. The system andmethod should be efficient, highly adaptable and easy to implement in avariety of networks. The system and method should also providemultilevel oversubscription. The present invention addresses such aneed.

SUMMARY OF THE INVENTION

[0009] The present invention is directed to a method and system foroversubscribing bandwidth in a communication network. The methodcomprises receiving data flow from a plurality of sources in anoversubscription module in the network, wherein the oversubscriptionmodule comprises a plurality of entry meters and at least oneoversubscription meter. The method further includes policing in an entrymeter the data flow from a source and generating an output flow, whereinthe entry meter enforces a service agreement between the source and thenetwork, policing the output flow from the entry meter in the at leastone oversubscription meter, wherein the oversubscription meter enforcesan oversubscription flow agreement, and generating an output flow fromthe at least one oversubscription meter that is transmitted through thenetwork.

[0010] In a preferred embodiment of the present invention, eachoversubscription meter reserves bandwidth to forward all high prioritypackets in the output flow from the meter and oversubscribes bandwidthfor low priority packets. Accordingly, network resources can beoversubscribed at multiple levels, while ensuring that all high prioritypackets are transmitted through the network.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a block diagram of a connection-less informationdistribution network in which the present invention could be implementedin accordance with a preferred embodiment.

[0012]FIG. 2 is a block diagram of the oversubscription module 50according to a preferred embodiment of the present invention.

[0013]FIG. 3 is a block diagram of the oversubscription module 100according to a preferred embodiment of the present invention.

[0014]FIGS. 4A and 4B are flowcharts illustrating a process foroverscribing the network according to a preferred embodiment of thepresent invention.

[0015]FIG. 5 is a block diagram of an oversubscription module 500according to a preferred embodiment of the present invention thataccompanies Example 1.

[0016]FIG. 6 is a block diagram of an oversubscription module 600according to a preferred embodiment of the present invention thataccompanies Example 2

DETAILED DESCRIPTION

[0017] The present invention relates to resource management in acommunication network and more particularly to a method and system foroversubscribing bandwidth in a communication network. The followingdescription is presented to enable one of ordinary skill in the art tomake and use the invention and is provided in the context of a patentapplication and its requirements. Various modifications to the preferredembodiment(s) and the generic principles and features described hereinwill be readily apparent to those skilled in the art. For instance,while the discussion will be primarily focused on connection-lessnetworks, such as an IP network, those skilled in the art will readilyappreciate that the principles can be applied to connection-orientednetworks as well. Thus, the present invention is not intended to belimited to the embodiment(s) shown but is to be accorded the widestscope consistent with the principles and features described herein.

[0018] To describe the general environment of the present invention,please refer to FIG. 1, which is a block diagram of a connection-lessinformation distribution network 10. As is shown, the distributionnetwork 10 includes a plurality of users or sources 20 a, 20 b . . . 20n that transmit data flow to a network 22. In the following discussion,the term “flow” is used to indicate a stream of data packets, e.g., IPpackets. Thus, a group of packets transmitted by a source (e.g., 20 a)to a network 22 is collectively referred to as “flow,” and isrepresented by the arrow between the source 20 a and the network 22. Thenetwork 22 typically collects the flow from the sources 20 a, 20 b . . .20 n, and forwards the flow to their respective destinations 40 a, 40 b,. . . 40 n, or aggregates flow and forwards the aggregated flow to anext network 30.

[0019] As stated above, the network 22 can allocate a certain level ofbandwidth for data flow originating from a source 20 a. A serviceagreement between the source 20 a and the network 22 sets forth theamount of bandwidth, if any, dedicated to data flow from that source 20a. As stated earlier, this dedicated bandwidth is referred to as the“Committed Information Rate” (CIR), and is measured in bytes of IPpackets per second. Data flow within the CIR is generally designated as“high priority.” In some instances, the service agreement will indicatethat no bandwidth will be reserved for a particular source 20 b, e.g.,CIR=0. In this case, data flow from this particular source 20 b is ofthe “best effort” type, i.e., the network 22 will make a best effort toforward the data flow.

[0020] In addition to reserving bandwidth for a source 20 a, the networkcan also typically designate an additional amount of bandwidth for“bursts” of data. This additional amount of bandwidth is referred to asa “Peak Information Rate” (PIR). The PIR is the maximum level ofbandwidth that is provided by the network 22 for the source 20 a. Dataflow exceeding the CIR but below the PIR is generally designated as“best effort” or “low priority.” Data flow exceeding the PIR istypically discarded. Generally, the PIR is greater than zero and isgreater than or equal to the CIR.

[0021] Thus, for each source 20 a, 20 b, . . . 20 n, the network 22provides a minimum amount of bandwidth (CIR), which may or may not bereserved, and a maximum amount of bandwidth (PIR) for incidental burstsof flow. In an oversubscription system and method of the presentinvention, the bandwidth corresponding to the PIR is oversubscribed viaan oversubscription module 50.

[0022] Referring again to FIG. 1, the network 22 includes anoversubscription module 50 through which all the data flow from eachsource 20 a, 20 b, . . . 20 n passes. According to a preferredembodiment of the present invention, the oversubscription module 50ensures that high priority data flow from each source 20 a, 20 b, . . .20 n is forwarded through the network 22. The oversubscription module 50discards data flow that violates the service agreement between a source20 a and the network 22. To the extent PIR bandwidth is available, theoversubscription module 50 will forward low priority data flow throughthe network 22. Low priority data flow exceeding available bandwidth isdiscarded. While the oversubscription module 50 is shown as a standalone module in FIG. 1, those skilled in the art would appreciate thatthe oversubscription module 50 can be implemented in a separate server(not shown) or in a dedicated network processor (not shown).

[0023]FIG. 2 is a block diagram of the oversubscription module 50according to a preferred embodiment of the present invention. As isshown, the oversubscription module 50 comprises a plurality of cascadedmeters 60. Each meter receives flow (e.g., F1, F2, F1′, F2′), policesthe flow according to a flow agreement, and generates an output flow(e.g., F1′, F2′, F5, F6), which is cascaded to a next level of meters60. In the oversubscription system and method of the present invention,each meter 60 transmits, at a minimum, any high priority flow itreceives. To do this, each meter 60 differentiates between high and lowpriority flow and generates its output flow based on such priority.

[0024] In a preferred embodiment, the meters 60 are modeled according tothe meter in a Two Rate Three Color Marker, as described in Request forComments: 2698 (Heinanen & Guerin Sept. 1999) (“RFC 2698”) andincorporated herein by reference. The Two Rate Three Color Marker is apolicing circuit that enforces a service agreement between a source 20 aand the network 22. The policing circuit includes a meter that meterseach packet in the flow as it enters the network 22, and a marker thatmarks the packets either green, yellow, or red. The meter calculateswhat the color of the packet should be by running a policing algorithm,which is based on the incoming flow and the service agreement. Thecalculated color can also be dependent on the input color of the packet.Meters that consider the input color of the packet are referred to as“color-aware,” while those that do not are referred to as “color-blind.”

[0025] The policing algorithm applied by the meter generallyincorporates the service agreement, which at a minimum, establishes theagreed CIR and PIR for the flow. In general, a packet will be red if theflow exceeds the PIR, yellow if the flow exceeds the CIR but is lessthan the PIR, and green if the flow is less than or equal to the CIR.Green packets are high priority traffic, e.g., CBR traffic, and yellowpackets are low priority traffic, e.g., best effort. Red packets arediscarded.

[0026] To describe better the method and system of the presentinvention, please refer now to FIG. 3 and FIGS. 4A and 4B. FIG. 3 is ablock diagram of the oversubscription module 100 according to apreferred embodiment of the present invention, and FIGS. 4A and 4B areflowcharts illustrating a process for oversubscribing the networkaccording to a preferred embodiment of the present invention. As isshown in FIG. 3, the oversubscription module 100 comprises a pluralityof entry meters, e.g. 110 a, 110 b, 110 c, 110 d, a first level ofoversubscription meters 120 a, 120 b, and a second leveloversubscription meter 130 a.

[0027] The process begins in step 310, whereby each entry meter 110a-110 d receives data flow (F1, F2, F3, F4) from different sources (notshown) (FIG. 4A). The entry meters can be either color-aware orcolor-blind. Each entry meter (e.g., 110 a) calculates the color of eachpacket in the flow based on a service agreement between the source ofthe flow (F1) and the network 22 in step 320. Thus, the configuration ofthe entry meter (110 a) reflects directly the service agreement. Thecalculated color is related to the packet's priority relative to themeter 110 a, and the color is referred to as the packet's cascadedcolor. It is important to note that the calculated color is associatedwith each packet and that the packet is not marked. In other words,unlike the policing circuit described in RFC 2698, each packet is notrecolored with the cascaded color.

[0028] In step 325, the entry meter 110 a generates an output flow(F1.a). Depending on the service agreement and the input flow F1, theoutput flow (F1.a) can include green packets (high priority), yellowpackets (low priority), or both. Red packets are discarded, andtherefore, not included in the output flow (F1.a). In step 330, theoutput flow (F1.a) is aggregated with output flows from other entrymeters (e.g., F1.b) and forwarded to one of a plurality of first leveloversubscription meters (120 a, 120 b). For example, in FIG. 3, outputflows F1.a and F1.b from entry meters 110 a and 110 b, respectively, areaggregated and forwarded to first level oversubscription meter 120 a,while the remaining outputted flows F1.c and F1.d are aggregated andforwarded to first level oversubscription meter 120 b. Those skilled inthe art would readily recognize that various flow patterns are possible,and that the present invention is not limited to the flow patternillustrated in FIG. 3.

[0029] In a preferred embodiment, each of the oversubscription meters(120 a, 120 b, 130 a) is color-aware. Accordingly, once the aggregatedflow (e.g., F1.a+F1.b) is received by the first level oversubscriptionmeter (e.g., 120 a) in step 340 (FIG. 4B), it considers each packet'scascaded color as it recalculates the color of each packet in the flow(F1.a+F1.b) according to an oversubscription flow agreement in step 350.An output flow (F2.a) is generated in step 355.

[0030] In step 360, it is determined whether another first leveloversubscription meter exists. If at least one other first leveloversubscription meter exists, the output flow (F2.a) from the firstlevel oversubscription meter 120 a is aggregated with flow from theother first level oversubscription meters, e.g., F2.b, in step 370. Instep 380, the aggregated flow (F2.a+F2.b) is forwarded to a next leveloversubscription meter 130 a, and steps 340-360 are repeated. If othersame level oversubscription meters do not exist, the output flow (F3.a)is transmitted through the network in step 390. While FIG. 4 illustratestwo levels of oversubscription, e.g., meters 120 a, 120 b and 130 a,those skilled in the art would readily appreciate that any number oflevels of oversubscription can be implemented depending on system needs.

[0031] In a preferred embodiment, the oversubscription flow agreementsfor the oversubscription meters 120 a, 120 b, 130 a allow a serviceprovider to oversubscribe the network 22, while ensuring thetransmission of high priority flow from its customers. To accomplish thelatter, each oversubscription flow agreement sets aside enough bandwidthto handle all packets having a cascaded green color. In particular, theCIR is at least that of the summation of CIRs of the previous meters.For example, the CIR for oversubscription meter 120 a would be at leastthe summation of the CIRs for entry meters 10 a and 110 b. Theoversubscription flow agreement also defines the degree ofoversubscription in the network by controlling the PIR for theoversubscription meter 120 a. Here, in order to oversubscribe PIRbandwidth, the PIR is less than the summation of PIRs for the previousmeters. Preferably, the PIR is equal to at least the highest PIR of theprevious meters.

[0032] Referring again to FIG. 2, it is important to note that eachmeter 60 associates a color with each packet and does not actually markthe packet. In other words, unlike the policing circuit described in RFC2698, each packet is not recolored with the cascaded color. Thus, if apacket is part of the flow (F7) exiting the oversubscription module 50,it retains its original color regardless of its cascaded color. In thismanner, the oversubscription module 50 oversubscribes the network 22without affecting the packets that are transmitted over the network 22.

[0033] To understand better the operation of the present invention,please refer to the following examples and accompanying Figures.

EXAMPLE 1

[0034]FIG. 5 is a block diagram of an oversubscription module 500according to a preferred embodiment of the present invention thataccompanies Example 1. Assume input flows F1.1, F1.2 and F1.3 are ofbest effort type. In this case, no bandwidth is reserved for best effortflow. Accordingly, the service agreements for the entry meters (P1.1,P1.2 and P1.3) define CIR=0, PIR=30. A service provider wishes toaggregate the flows (F1.1, F1.2 and F1.3) such that the outgoing flow(F′2.1) is of type CBR. The oversubscription meter P2.1 will have anoversubscription flow agreement that defines CIR=PIR=30.

[0035] Given this configuration, consider the following flow:

[0036] F1.1=F1.2=F1.3=15 green best effort packets

[0037] Because CIR<15<PIR, each of the packets will have a cascadedcolor yellow. The output flow (F′1.1, F′1.2, F′1.3) from each entrymeter (P1.1, P1.2, P1.3) will include 15 yellow packets. Therefore, theaggregated flow will include 45 yellow packets, which are passed to theoversubscription meter P2.1. Here, the oversubscription meter P2.1 willreturn 30 yellow packets and 15 red packets because PIR=30. The 15 redpackets will be discarded and the outgoing flow (F′2.1) will include 30green packets. Preferably, the outgoing flow (F′2.1) is evenlydistributed between the three original flows (F1.1, F1.2, F1.3).

[0038] Now consider the following flow for the same configuration:

[0039] F1.1=F1.2=15 green best effort; F1.3=0

[0040] As before, output flow (F′1.1, F′1.2) from each entry meter(P1.1, P1.2) will include 15 yellow packets. Nevertheless the aggregatedflow now comprises 30 yellow packets. The oversubscription meter P2.1will pass all 30 packets. Thus, when resources are available (e.g., PIRbandwidth), the maximum number of packets will pass.

EXAMPLE 2

[0041]FIG. 6 is a block diagram of an oversubscription module 600according to a preferred embodiment of the present invention thataccompanies Example 2, where like components share like references.Assume input flow F1.1 is of type CBR and F1.2 is of best effort type.The service agreement for the entry meter P1.1 defines CIR=PIR=10, andthe service agreement for entry meter P1.2 defines CIR=0, PIR=30. Aservice provider wishes to aggregate the flows (F1.1, and F1.2) suchthat the outgoing flow (F′2.1) is of type VBR. The oversubscriptionmeter P2.1 will have an oversubscription flow agreement that definesCIR=10, PIR=30. Note that the CIR should be at least 10 to ensurequality of service for the CBR flow F1.1.

[0042] Given this configuration, consider the following flow:

[0043] F1.1=15 green CBR; F1.2=25 green best effort

[0044] Output flow (F′1.1) from entry meter P1.1 comprises 10 greenpackets (5 red packets discarded). Output flow (F′1.2) from entry meterP1.2 comprises 25 yellow packets. Outgoing flow (F′2.1) from theoversubscription meter P2.1 comprises 30 green packets the 10 cascadedgreen packets and 20 cascaded yellow packets. Five additional redpackets are discarded.

[0045] In this case, high priority flow (i.e., 10 green packets) istransmitted and unaffected by the oversubscription of PIR bandwidth. Tothe extent that PIR bandwidth is available, low priority flow (e.g., 20yellow packets) will also be transmitted.

[0046] Now consider the following flow for the same configuration:

[0047] F1.1=0; F1.2=25 green best effort packets

[0048] The aggregated flow passed to the oversubscription meter P2.1comprises 25 yellow packets. The outgoing flow (F′2.1) comprises 25green best effort packets. In this case, no high priority flow ispresent, and therefore, non-utilized resources can be used to transmitlow priority flow.

[0049] Through aspects of the method and system of the presentinvention, network resources can be oversubscribed at multiple levels,while ensuring that all high priority flow is transmitted through thenetwork. By utilizing meters modeled after the meter in a Two Rate ThreeColor Marker, the oversubscription module is platform independent andcompatible for connection-less, as well as connection oriented networks.The method and system of the present invention is easily implementedbecause the Two Rate Three Color Marker is a well known policing circuitand the policing algorithm is not modified.

[0050] Although the present invention has been described in accordancewith the embodiments shown, one of ordinary skill in the art willreadily recognize that there could be variations to the embodiments. Forexample, although the preferred embodiment utilizes a Two Rate ThreeColor Marker meter, any type of policing meter that has the capabilityto differentiate between high and low priority flow, e.g., a Single RateThree Color Marker (RFC 2697), is suitable. Those variations would bewithin the spirit and scope of the present invention. Accordingly, manymodifications may be made by one of ordinary skill in the art withoutdeparting from the spirit and scope of the appended claims.

What is claimed is:
 1. A method for oversubscribing bandwidth in acommunication network comprising the steps of: (a) receiving a data flowfrom a plurality of sources in an oversubscription module in thenetwork, wherein the oversubscription module comprises a plurality ofentry meters and at least one oversubscription meter; (b) policing in anentry meter data flow from a source and generating an output flow,wherein the entry meter enforces a service agreement between the sourceand the network; (c) policing the output flow from the entry meter inthe at least one oversubscription meter, wherein the at least oneoversubscription meter enforces an oversubscription flow agreement; and(d) generating an output flow from the at least one oversubscriptionmeter that is transmitted through the network.
 2. The method of claim 1,wherein the plurality of entry meters and the at least oneoversubscription meter comprises a Two Rate Three Color Marker meter. 3.The method of claim 2, wherein the data flow comprises a plurality ofpackets and policing step (b) comprises: (b1) applying a Two Rate ThreeColor Marker policing algorithm based on the service agreement; and (b2)calculating a color associated with each packet in the data flow,wherein the associated color indicates a priority level for each packet.4. The method of claim 3, wherein the calculating step (b2) comprises:(b2i) if the packet is a high priority packet, associating the packetwith green; (b2ii) if the packet is a low priority packet, associatingthe packet with yellow; and (b2iii) if the packet exceeds an allottedbandwidth for the source, associating the packet with red.
 5. The methodof claim 4, wherein the policing step (b) further comprises: (b3)discarding the packet if the associated color is red; and (b4)forwarding the packet if the associated color is yellow or green in theoutput flow.
 6. The method of claim 5, wherein the policing step (c)comprises: (c1) aggregating the output flow from the entry meter with anoutput flow from at least one other entry meter and forwarding theaggregated flow to a first level oversubscription meter; (c2) applyingthe Two Rate Three Color Marker policing algorithm based on theassociated color of each packet and on the oversubscription flowagreement, wherein the oversubscription flow agreement oversubscribes aPeak Information Rate (PIR) bandwidth for the oversubscription meter;and (c3) calculating a reassociated color for each packet in theaggregated flow.
 7. The method of claim 6, wherein the calculating step(c3) comprises: (c3i) if the associated color is green, reassociatingthe packet with green; (c3ii) if the associated color is yellow and PIRbandwidth is available, reassociating the packet with yellow; else(c3iii) reassociating the packet with red.
 8. The method of claim 7,wherein the policing step (c) further includes: (c4) discarding thepacket if the reassociated color is red; else (c5) forwarding the packetin an output flow from the first level oversubscription meter.
 9. Themethod of claim 8, wherein the generating step (d) comprises: (d1) if atleast one other first level oversubscription meter exists, aggregatingthe output flow from the first level oversubscription meter with anoutput flow from the at least one other first level oversubscriptionmeter, forwarding the aggregated flow to a next level oversubscriptionmeter and repeating steps (c2) through (c5) for the next leveloversubscription meter; else (d2) transmitting the output flow from theoversubscription meter through the network.
 10. The method of claim 6,wherein the oversubscription flow agreement defines a CommittedInformation Rate (CIR) bandwidth to forward all green packets in theaggregated flow.
 11. An oversubscription module for oversubscribingbandwidth in a communication network comprising: a plurality of entrymeters, wherein each entry meter is configured to police data flow froma source by enforcing a service agreement between the source and thenetwork to generate an output flow; and at least one oversubscriptionmeter, wherein the at least one oversubscription meter is configured topolice the output flow from an entry meter by enforcing anoversubscription flow agreement.
 12. The oversubscription module ofclaim 11, wherein the plurality of entry meters and the at least oneoversubscription meter comprises a Two Rate Three Color Marker meter.13. The oversubscription module of claim 12, wherein the data flowcomprises a plurality of packets and each of the plurality of entrymeters is configured to apply a Two Rate Three Color Marker policingalgorithm based on the service agreement, and to calculate a colorassociated with each packet in the data flow, wherein the associatedcolor indicates a priority level for the packet.
 14. Theoversubscription module of claim 13, wherein each of the plurality ofentry meters is configured to discard the packet if the associated coloris red and forward the packet if the associated color is yellow or greenin the output flow.
 15. The oversubscription module of claim 14 furthercomprising means for aggregating the output flow from the entry meterwith an output flow from at least one other entry meter and forwardingthe aggregated flow to a first level oversubscription meter.
 16. Theoversubscription module of claim 15, wherein the first leveloversubscription meter is configured to apply the Two Rate Three ColorMarker policing algorithm based on the associated color of each packetand on the oversubscription flow agreement, whereby the oversubscriptionflow agreement oversubscribes a Peak Information Rate (PIR) bandwidthfor the oversubscription meter, to calculate a reassociated color foreach packet in the aggregated flow, and to generate an output flow. 17.The oversubscription module of claim 16 further comprising means toaggregate the output flow from the first level oversubscription meterwith an output flow from one other first level oversubscription meter,and means to forward the aggregated flow to a next leveloversubscription meter, wherein the next level oversubscription meter isconfigured similarly to the first level oversubscription meter.
 18. Theoversubscription module of claim 17, wherein if the output flow from anoversubscription meter cannot be aggregated with the output flow fromanother oversubscription meter, the output flow is transmitted throughthe network.
 19. The oversubscription module of claim 11, wherein eachoversubscription meter is configured to forward all high prioritypackets in the output flow from the entry meter.